﻿#region 程序集引用
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
#endregion

#region 版权注释
/*===========================================================================
// Copyright (C) 2017 Zhang.cn，并保留所有 
// 作者：李祖武 QQ:6630641
// 创建日期：2019-06-29
// 功能描述： 根据经纬度计算2点距离
===========================================================================*/
#endregion

namespace Zhang.Utils
{
    /// <summary>
    /// * 计算两个经纬度之间的距离
    /// </summary>
    public static class CalulateTwoLatLon
    {       
        private static double EARTH_RADIUS = 6378.137;//地球半径,单位千米
        /// <summary>
        /// 
        /// </summary>
        /// <param name="d"></param>
        /// <returns></returns>
        private static double rad(double d)
        {
            return d * Math.PI / 180.0;
        }


        /// <summary>
        /// 两个经纬度的距离
        /// </summary>
        /// <param name="lat1">第一个纬度</param>
        /// <param name="lng1">第一个经度</param>
        /// <param name="lat2">第二个纬度</param>
        /// <param name="lng2">第二个经度</param>
        /// <returns></returns>

        public static double getDistance(double lat1, double lng1, double lat2, double lng2)
        {
            double radLat1 = rad(lat1);
            double radLat2 = rad(lat2);
            double a = radLat1 - radLat2;
            double b = rad(lng1) - rad(lng2);

            double s = 2 * Math.Asin(Math.Sqrt(Math.Pow(Math.Sin(a / 2), 2) +
                    Math.Cos(radLat1) * Math.Cos(radLat2) * Math.Pow(Math.Sin(b / 2), 2)));
            s = s * EARTH_RADIUS;
            s = Math.Round(s * 10000) / 10000;
            return s;

        }
    }
}
